Passerine - Origin and Evolution

Origin and Evolution

The evolutionary history of the passerine families and the relationships among them remained rather mysterious until the late 20th century. In many cases, passerine families were grouped together on the basis of morphological similarities which, it is now believed, are the result of convergent evolution, not a close genetic relationship. For example, the "wrens" of the northern hemisphere, those of Australia, and those of New Zealand look very similar and behave in similar ways, and yet belong to three far-flung branches of the passerine family tree; they are as unrelated as it is possible to be while remaining Passeriformes.

Much research remains to be done, but advances in molecular biology and improved paleobiogeographical data are gradually revealing a clearer picture of passerine origins and evolution that reconciles molecular affinities, the constraints of morphology and the specifics of the fossil record. It is now thought that the first passerines evolved in Gondwana at some time in the Paleogene, maybe around the Late Paleocene some 60–55 mya. The initial split was between the Tyranni, the songbirds, the Eurylaimides and the New Zealand "wrens", which must have diverged during a short period of time (some million years at most). The Passeriformes apparently evolved out of a fairly close-knit clade of "near passerines" which contains such birds as the Piciformes and Coraciiformes.

A little later, a great radiation of forms took place out of Australia-New Guinea: the Passeri or songbirds. A major branch of the Passeri, "Parvorder Passerida", emerged either as the sister group to the basal lineages and corvoids ("Parvorder Corvida"), or more likely as a subgroup of it, and expanded deep into Eurasia and Africa, where there was a further explosive radiation of new lineages. This eventually led to three major passeridan lineages comprising about 4,000 species, which in addition to the corvoidan clade and numerous minor lineages make up songbird diversity today. There has been extensive biogeographical mixing, with northern forms returning to the south, southern forms moving north, and so on.

Read more about this topic:  Passerine

Famous quotes containing the words origin and/or evolution:

    There are certain books in the world which every searcher for truth must know: the Bible, the Critique of Pure Reason, the Origin of Species, and Karl Marx’s Capital.
    —W.E.B. (William Edward Burghardt)

    The more specific idea of evolution now reached is—a change from an indefinite, incoherent homogeneity to a definite, coherent heterogeneity, accompanying the dissipation of motion and integration of matter.
    Herbert Spencer (1820–1903)